1. Field of Invention
The present invention relates to light weight energy-beam settable resin coating compositions, a method for forming such coatings, and articles of manufacture formed therefrom.
2. Description of Related Art
The air-blown fiber method, which is a new method of laying a communication line material, is disclosed, for example, in Japanese Patent Unexamined Publication No. Sho-59-104607. In such a method, a communication line material is sent by pressure so as to be laid into a duct line laid in advance, by means of an air flow, for example, by using a pressure-sending apparatus 31 shown in FIG. 3. Here, in the drawing, a feed head 34 is attached on an end portion of the duct line 32; drive wheels 35 and 36 send a communication line material 33; and an air lead-in inlet 37 leads in air for sending the communication line material 33 by pressure. Further, an air seal 38 prevents leakage of air from an inlet portion of the feed head 34 for the communication line material 33. The air seal 38 is provided because the duct line 32 is so long that there is a large loss of pressure.
It is necessary to make the communication line material 33 used in such a method light-weight and to make the surface area large so that the communication line material 33 can be efficiently sent by pressure created by an air flow. For this purpose, the configuration shown in FIG. 4 has been proposed.
In the communication line material 33 shown in FIG. 4, a bundle of seven optical fibers 41 are coated by a polypropylene layer 42, and the polypropylene layer 42 is coated with a foam polyethylene layer 43.
When foam polyethylene is used to form the foam polyethylene layer 43 of the communication line material 33, however, a problem results because the foam polyethylene is apt to be influenced by the cooling temperature, the temperature distribution in the inside of the extruded material, or dimensional variations in the under-layer to be coated. That is, there is a problem either because the degree of foaming of the foam polyethylene is apt to vary, thereby changing the outer diameter of the foam polyethylene layer 43, or because the thickness of the foam layer is apt to vary as a result of the circumferential temperature distribution in the die which extrudes the layer. As a result, for example, there is a problem of blocking at the portion of the air seal 38 of the pressure-sending apparatus.
Further, since the actual foaming of the foam polyethylene occurs gradually, an extended cooling period is necessary after performing the extrusion-coating with the foam polyethylene. Also, as shown in FIG. 5, it is necessary to provide a long cooling line 54 between a die 52 of an extruder 51 and a take-up machine 53. Thus the extended cooling process results in poor productivity.
Moreover, since there is little adhesion between the coating layer of a foam resin such as foam polyethylene and the under-layer, slippage results between the foam coating layer and the under-layer.